Vitamin supplements, smoking and lung cancer risk

I just read that there is a greater risk of lung cancer for smokers who take vitamin supplements. I smoke and have been taking beta carotene for about 4 months because I was told it would reduce my risk – I am now really worried.

This page tells you about research into vitamin supplements and risk of lung cancer. There is also information about trying to give up smoking. You can use these links to take you straight to sections about

• Taking beta carotene supplements
• What beta carotene is
• Research into beta carotene, vitamin E and lung cancer
• Trying to stop smoking

It is probably first best to reassure you that there is no evidence to suggest that you have increased your risk of lung cancer by taking beta carotene for such a short time. But researchers recommend that supplements are not used as a way of reducing lung cancer risk. As we are sure you know, the best way to decrease your risk of getting lung cancer is to give up smoking. This can be more easily said than done though.

Beta carotene is a substance found mainly in vegetables that are deep yellow, orange or dark green – for example, carrots, spinach and squash. It is converted to vitamin A in the body. Doctors have recently been looking into foods containing beta carotene, other vitamins and lung cancer. Studies have linked a high intake of these foods with a reduced risk of cancer, particularly lung cancer.

Fresh fruit and vegetables are thought to help prevent cancer because they contain chemicals that can prevent cell damage, such as the anti oxidant vitamins A, C and E, flavenoids and other chemicals. But if you smoke, it's no good carrying on and just eating a lot of fruit and vegetables as well. The most important thing by far is to stop smoking.

Clinical trials have shown that long term use of some supplements in smokers can increase lung cancer risk.

One study called the ‘Alpha Tocopherol, Beta Carotene Cancer Prevention Study’, looked at whether taking alpha tocopherol (a form of vitamin E) and 20 mg of beta carotene daily reduced the risk of lung cancer. The study recruited 29,133 male smokers. A computer randomised people taking part into groups. One group took pills containing alpha tocopherol. Another group took pills containing beta carotene. One group took pills containing both. The others took a dummy pill (placebo). They took the pills daily for between 5 and 8 years. In this study 18% more lung cancers developed in the people taking the alpha tocopherol and beta carotene pills. This was the opposite of what the researchers expected.. In the eight years following the trial, the people who took beta carotene had a higher chance of dying from lung cancer than men taking the placebo. Vitamin E did not seem to have any effect on lung cancer risk in this trial.

Another study called the ‘Beta Carotene and Retinol Efficacy Trial’(CARET), looked at whether beta carotene and retinol (vitamin A) could prevent cancer in men and women smokers and ex smokers. The people in the trial were aged from 45 to 69. This trial was also randomised and some participants took a placebo pill. After an average of 4 years of taking the pills, there were 28% more cases of lung cancer diagnosed in people taking the supplements. But 6 years after stopping the pills, the risk of lung cancer had decreased and was almost the same as for people who had not taken the supplements.

It is not clear what effect vitamin supplements may have in non smokers. The VITamins And Lifestyle (VITAL) study reported in 2009. It looked at the effect of beta carotene, retinol, vitamin A, lutein, and lycopene supplements on lung cancer risk. 77,126 people aged between 50 and 76, in Washington State, USA filled in a questionnaire. Some questions asked about whether they had taken dietary supplements, what doses, and how long they took them for. People in the study were monitored and those who had taken beta carotene, retinol, or lutein supplements for more than a few years had a higher risk of lung cancer.

Not all studies have shown that beta carotene increases the risk of lung cancer in smokers though. The Physicians Health Study was a trial with 22,071 American male doctors. Only 11% of these doctors were smokers. The purpose of the study was to test whether a beta carotene supplement reduced the risk of cancer and heart disease. The Physician's Health Study finished at the end of 1995. The results showed that there was no benefit or harm to people taking beta carotene supplements for more than 12 years.

From research it is clear that high dose beta carotene supplements can increase the risk of lung cancer especially in smokers. Some other vitamins and minerals may also be harmful but more research is needed to be sure.

There is no evidence to suggest that smokers should cut down on foods that contain high levels of beta carotene. It may be that a component of these foods other than beta carotene helps to protect against cancer. Or, it may be that the whole food is better than a supplement.

We appreciate that it is not always an easy thing to do, but the best advice to smokers, who want to reduce their risk of lung cancer, is to stop smoking. It is never too late to stop smoking, although the sooner you do the greater the long term benefits for your health. There are also instant benefits to be had from giving up smoking, like improvements in your breathing. Also, your sense of smell and taste will improve and skin problems may clear up.

The physical craving for a cigarette can disappear as soon as one week after giving up. But the psychological cravings may last for much longer. Help is available to improve your chance of giving up smoking successfully – contact Quitline on 0800 002200 or talk to your doctor. The National Institute for Health and Clinical Excellence (NICE) issued guidance in July 2007 that varenicline should be available free on the NHS for people who want to give up smoking. Varenicline is also known as Champix and is a tablet you take once or twice a day to help you stop smoking. NICE say that it should be prescribed alongside counselling and support. Nicotine replacement products have also helped many people give up. You can buy them at your chemist or ask your doctor about getting them on prescription. You can talk to your pharmacist to find out which product is best for you.

Cancer Research UK produces a leaflet called, Wish you could give it up?. You can download the leaflet from the Cancer Research UK website. The website also has information on how to stop smoking and where to ask for help.